1. Field of the Invention
The present invention relates to a vehicle seat by which a user can twist his or her body toward the backside and which is comfortable to sit in.
2. Related Art
Conventionally, vehicle seats have been subjected to various technical developments. One of such techniques provides, for example, a known automobile seat structured so that a backrest is divided to an upper half backrest and a lower half backrest and the upper half backrest is attached to the lower half backrest so that the former can be rotated to the latter around a vertical axis line via a pivot point (see Patent Publication 1).
The automobile seat as described above also allows, when the driver checks the backside or takes a baggage or the like on a backseat, a driver to twist his or her upper body toward the backside in accordance with the rotation of the upper half backrest.
[Patent Publication 1] Japanese Utility Model Unexamined Publication No. 64-002632
By the way, the automobile seat is designed so that a regular position-lock device is provided at a side face of the lower half backrest. This regular position-lock device can be unlocked by a one-touch operation by depressing a lever. By unlocking the regular position-lock device, the upper half backrest can be rotated in the left-and-right direction.
However, this regular position-lock device must be unlocked by manually depressing the lever. Furthermore, this regular position-lock device requires a user to extend his or her arm to the lever at the side face of the lower half backrest, which may cause a situation where the user requires a long time to unlock the device particularly for an operation for moving the vehicle backward.
On the other hand, although the above-described structure of the automobile seat allows the upper half backrest to be rotated to the lower half backrest, this structure does not have a rotation restoration force. Thus, when the upper half backrest is returned to the regular position, this structure has required the driver to return his or her upper body to the original position by rotating his or her body in the reverse direction.
Furthermore, this structure allows only the upper half backrest to be rotated in the left-and-right direction as described above. This has caused an inconvenience where, when the driver twists the upper body, the upper half backrest cannot be rotated in a manner adapted to the contour of the driver, thus failing to provide a fit with the back face of the driver.
Due the situation as described above, such a vehicle seat has been desired that is different from the conventional one in that a driver can twist his or her body toward the backside without requiring a lock mechanism such as the regular position-lock device; in that the vehicle seat can be fit with the back face of the driver; in that the vehicle seat has a rotation restoration force; and in that the vehicle seat is comfortable to sit in.